Using Observational Campaigns to Explore Evolving VOC Composition across the Eastern US

Ozone production is non-linearly dependent upon nitrogen oxides (NOx) and Volatile Organic Compound (VOC) concentrations. During warmer months in the Eastern US, biogenically produced isoprene is the dominant VOC in the atmosphere. It has a lifetime of only a few hours due to rapid oxidation with OH. This quick breakdown results in isoprene having the ability to produce on the order of 10 ozone molecules per isoprene molecule under ideal conditions and is therefore a major contributor to ozone formation over much of the Eastern US. In regions where isoprene is depleted like over large bodies of water, or before trees have their leaves, the dominant VOC can shift from isoprene (biogenic) to longer lived VOCs like those with anthropogenic sources.

We use observations from a variety of aircraft campaigns and ground based networks to analyze the Ozone Formation Potential (OFP) of primary VOCs as a function of altitude. Since formaldehyde (HCHO) is a common daughter product of larger VOCs and it is readily observed from space, we compare the OFP of HCHO with other observed VOCs to determine where HCHO accounts for most of the OFP and is therefore a good representation of total VOCs. This analysis provides insight into developing effective air quality policy to regulate ozone as VOC composition evolves in the Eastern US.